feat(dashboard): unify Top Talkers with NetFlow traffic data (v0.13.1-beta)

The Dashboard "Top talkers" card and the Traffic page previously used
different data sources: the card ranked clients by device-reported
since-connection byte counters (wireless-centric, reset on reconnect, no
time window), while the Traffic page uses NetFlow-measured bytes.

The card now prefers the NetFlow top-clients data (last 24h — identical
numbers to the Traffic page) and falls back to the legacy counters only
when the collector has no data, with the source labeled in the card
header ("by bytes · 24h" vs "since connection"). Rows now click through
to the client detail page.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mikrotik-manager-backend",
-  "version": "0.13.0-beta",
+  "version": "0.13.1-beta",
   "description": "Mikrotik Network Management Platform - Backend API",
   "main": "dist/index.js",
   "scripts": {